Evidence for the role of viruses and/or genetics in the etiology of cancer was provided in several studies. Analysis of data including HTLV-I antibody titers on serum samples from more than 42,000 individuals in various geographic locales suggested that in addition to Japan and the Caribbean Islands, HTLV-I was endemic in New Guinea and sub-Saharan Africa. Newly identified populations with antibodies reacting against HTLV-I antigens included Indians living in Florida and Panama. The etiologic role of the Epstein-Barr virus (EBV) in nasopharyngeal carcinoma was strengthened by the detection of EBV in biopsies from all American patients entered into a multicenter collaborative study, including all with the more differentiated form (WHO type I) of NPC which had been thought by many not to be EBV-associated. Specific findings involving the role of genetics in the etiology of human cancer included: 1) the first report on familial breast cancer in black Americans, 2) the detection of N-ras oncogene in a high frequency of patients with acute myelogenous leukemia, 3) the evaluation of a white family with an increased incidence of cancer which included three siblings with NPC, and 4) the identification of a family with a high frequency of immunologic and hematologic (including acute myelomonocytic leukemia) abnormalities that may be a previously undescribed entity similar to, but distinguishable from, Fanconi's anemia.